This invention relates to an improved resin hydrotreating process which maintains resin softening point and aromaticity as well as catalyst lifetime. The process is particularly useful for hydrotreating resins containing halogen residue.
Petroleum resin hydrogenation processes are well known. Hydrocarbon resins obtained from thermal or catalytic polymerization of olefin and diolefin containing streams are often dark in color which is undesirable for many applications. Hydrogenation processes are used to lighten the color and improve heat and ultraviolet light stabilities. Hydrogenation processes, however, have their own limitations. For example, catalytically polymerized resins may contain halogen residue derived from the catalyst. These catalyst residues tend to accumulate on the acidic surface of the hydrogenation catalyst. This accumulation in combination with hydrogenation conditions tends to hydrocrack the resin and deteriorate key resin properties such as resin softening point and reduces product yield. We have discovered a unique hydrogenation process that reduces resin color while maintaining softening point and catalyst life.
U.S. Pat. No. 4,629,766 describes a hydrogenation process intended for thermally polymerized resins that uses high hydrogen pressure to improve yields, color and heat stability.
U.S. Pat. No. 5,491,214 describes a batch hydrogenation process that uses specific catalysts designed to hydrogenate only color bodies in the resin without hydrogenating the resin""s carbon-carbon double bonds.
U.S. Pat. No. 5,552,363 describes a specific hydrogenation catalyst that is resistant to halogen contaminants in the resin. U.S. Pat. No. 5,820,749 also describes a specific hydrogenation catalyst designed primarily to increase productivity.
The processes described herein generally enable hydrotreatment of resins on a continuous basis without prior treatment of the resins to remove catalyst residues. Process conditions are provided for different types of resin to limit cracking of the resin backbone while improving the resin color. In particular the processes of this invention are directed to a one-step hydrogenation process comprising:
(a) introducing hydrocarbon resin having from about 50 ppm by weight to about 2000 ppm by weight of one or more halogen residues into a reactor, said resin having a softening point X, where X is a temperature of from about 70xc2x0 C. to about 150xc2x0 C.;
(b) hydrotreating the resin in the reactor with a catalyst using pressure of not more than 2000 psi for a time period of at least 800 hours at a temperature in the range of from about 100xc2x0 C. to about 350xc2x0 C. thereby producing at least 350 tons of polymer per ton of catalyst; and
(c) recovering from the reactor hydrotreated resin having a softening point Yxc2x0 C. of no less than Xxe2x88x928.
This invention is directed to processes for hydrotreating hydrocarbon resin or rosin under suitable hydrotreating conditions, with a mono or bi-metallic catalyst system based on Group 6,7,8,9,10 and 11 elements (IUPAC notation Handbook of Chemistry and Physics, 70th Ed., 1989/1990) supported on an acidic support such as alumina. Hydrocarbon resins prepared from catalytic or thermally polymerized petroleum feed streams and hydrogenated according to the invention exhibit lighter color compared to the original and with aromaticity, softening point properties equivalent to the original resin.
The catalytically polymerized resins obtained from the polymerization of C5-C10 with Friedel-Crafts or Lewis Acids catalysts and hence contain catalyst halogen residues. The processes described herein enable hydrotreatment of the resins on a continuous basis without prior treatment of the resins to remove catalyst residues. Process conditions are provided for different types of resin to limit cracking of the resin backbone while improving the resin color. Cracking deteriorates important physical properties such as resin softening point, molecular weights, decreases product yield and reduces effective catalyst life.
Although this hydrogenation process may be conducted batch-wise, it is uniquely suited to a one-step or one-stage, continuous, fixed-bed hydrogenation process. xe2x80x9cOne-stepxe2x80x9d or xe2x80x9cone-stagexe2x80x9d means that the entire hydrogenation is conducted in one reactor without further hydrogenation in a separate vessel and without any prior step to remove impurities such as halogen residues from the resin. Preferably the process is continuous and is conducted at a rate of at least 350 tons of polymer produced per ton of catalyst used for at least 800 hours, more preferably at least 1000 hours, even more preferably at least 1500 hours and most preferably at least 3000 hours.
In the most preferred process, hydrogenation is conducted using petroleum resins obtained from the cationic polymerization of steam-cracked naphtha using a Friedel-Crafts catalyst such as aluminum trichloride or boron trifluoride. Resins can also be obtained from thermal polymerization using cyclo-aliphatic or cyclo-aliphatic and aromatic feeds. The preferred resins are those known to be useful as tackifiers for adhesive applications and road-marking applications and polymer modification. Petroleum resins include hydrocarbon resins that have been modified with aromatic or terpene containing feedstream; hydrocarbon resins from pure aromatic monomers, the coumarone-indene resins and the polyterpenes resins. For additional description of feedstream derivation, monomer composition, methods of polymerization and hydrogenation, reference can be made to technical literature, e.g. Hydrocarbon Resins, Kirk-Othmer, Encyclopedia of Chemical Technology, 4th Ed. v.13, pp. 717-743. The natural resins, rosins including gum rosins, wood rosin, and tall oil rosins can also be hydrotreated according to this process.
The hydrogenation process of this invention is particularly useful for hydrotreating halogen containing resins. Resins produced by Friedel-Crafts polymerization typically contain between about 50 ppm by weight and about 2000 ppm halogen residue, some contain between about 1000 ppm by weight and about 1500 ppm by weight halogen residue. As used herein, xe2x80x9chalogen residuexe2x80x9d means any compound containing one or more halogen atoms.
Petroleum resins are typically produced by thermally or catalytically polymerizing petroleum fractions. These polymerizations may be batch, semi-batch or continuous. Petroleum fractions containing aliphatic C5 to C6 linear, branched, alicyclic monoolefins, diolefins, alicyclic C10 diolefins can be polymerized. The aliphatic olefins can comprise one or more natural or synthetic terpenes, preferably one or more of alpha-pinene, beta-pinene, delta-3-carene, dipentene, limonene or isoprene dimers. C8-C10 aromatic olefinic streams containing styrene, vinyl toluenes, indene, methyl-indenes can also be polymerized as such or in mixture with the aliphatic streams.
Thermal polymerization is usually carried out at a temperature between 160xc2x0 C. and 320xc2x0 C., e.g., at about 250xc2x0 C., for a period of 0.5 to 9 hours, typically 1.5 to 4 hours. Catalytic polymerization is usually carried out with a Friedel-Crafts or Lewis Acid catalyst such as metallic halides such as aluminum trichloride or boron trifluoride, aluminum tribromide or mixture thereof, as well as ternary complexes of the halides, aromatic compounds and hydrogen halides. A polymerization reaction is usually run at a temperature between xe2x88x9220xc2x0 C. to 200xc2x0 C., preferably between 0xc2x0 C. and 120xc2x0 C. and more preferably between 20xc2x0 C. and 80xc2x0 C. Catalytic polymerization is usually accomplished in a polymerization solvent and removal of solvent and catalyst by washing and distillation. The hydrotreating process of this invention is essentially useful for treating catalytically polymerized aliphatic or aromatic resins containing catalyst-derived halogen residue.
The polymeric resin so produced is dissolved in an inert, de-aromatized or non-de-aromatized hydrocarbon solvent such as Exxsol(trademark) or Varsol(trademark) or base white spirit in proportions varying from 10% to 60% and preferably in the region of 30% by weight polymer. Hydrogenation is then conducted in a fixed-bed, continuous reactor with the feed flow being either an upflow or downflow liquid phase or trickle bed operation.
Hydrogenation treating conditions generally include reactions ranging in temperature of from about 100xc2x0 C. to about 350xc2x0 C., preferably ranging from about 150xc2x0 C. to about 300xc2x0 C., more preferably ranging from about 160xc2x0 C. to about 270xc2x0 C. The hydrogen pressure within the reactor should not exceed more than 2000 psi, preferably no more than 1500 psi, and most preferably no more than 1000 psi. The hydrogenation pressure is, however, a function of the hydrogen purity and the overall reaction pressure should be higher if the hydrogen contains impurities to give the desired hydrogen pressure. Typically the optimal pressure used is between about 750 psi and 1500 psi, preferably between about 800 psi and about 1000 psi. The hydrogen to feed volume ratio to the reactor under standard conditions (25xc2x0 C., 1 atm Pressure) typically can range from about 20 to about 200.
Catalyst activity typically decreases over time due to carbonaceous deposition onto the catalyst support, this can be partially eliminated or removed by regenerating the catalyst bed with pressure hydrogen at temperatures between about 310xc2x0 C. and 350xc2x0 C. Pressures from 60 to 180 bar can be used. This regeneration is best accomplished in the absence of hydrocarbon feed to the reactor, e.g., during interruption of the hydrogenation process. The reactor is typically fed with an inert solvent such as Exxsol(copyright) or Varsol(copyright) during the regeneration process.
Catalysts employed for the hydrogenation of resins are typically supported monometallic and bimetallic catalysts systems based on Group 6,7,8,9,10 and 11 elements (IUPAC notation Handbook of Chemistry and Physics, 70th Ed., 1989/1990). Catalysts based on cobalt, nickel, tungsten, palladium, copper and/or zinc are particularly suitable. The catalyst preferably used in this process is hydrodesulphurization catalyst prepared by impregnating the oxides of nickel and tungsten onto an alumina support, preferably a high surface area alumina such as gamma alumina. The preferred components are nickel and tungsten on a gamma alumina support. The concentration of metals on the catalyst is important for good performance and ranges from 2 to 10, preferably 4 to 5, weight percent nickel and from 10 to 25, preferably 16 to 20 weight percent tungsten. The pore size distribution of the alumina support is also important to the performance of the catalyst. The catalyst is prepared such that the pore volume of the small pores in the 15-300 Angstrom radius range is less than 70% of the total pore volume whereas the large pores or channels having radii in the range of 10,000 to 75,000 A are at least 10% of the total pore volume between 10 and 75,000 Angstrom. This results in a fresh catalyst surface area of the support typically in the range of 120-300 m2/g.
Other suitable catalysts are detailed in U.S. Pat. No. 5,820,749 (fully incorporated herein by reference). Particularly suitable catalysts described in this patent include those comprising the metals nickel and/or cobalt and one or both of molybdenum or tungsten on a support comprising porous refractory substrate particles having: a) a mean maximum diffusion path length less than or equal to twice the hydraulic radius of the particle; b) a pore volume distribution wherein, i) pores having diameters  greater than 150,000 (1.5xc3x9710xe2x88x925 m) xc3x85 constitute greater than about 2% of the total volume, ii) pores having diameters  greater than 20,000 xc3x85 and less than 150,000 xc3x85 constitute greater than about 1% of the total volume, and iii) pores having diameters  greater than 2,000 xc3x85 (2.0xc3x9710xe2x88x927 m) and  less than 20,000 xc3x85 (2.0xc3x9710xe2x88x926 m) constitute greater than about 12% of the total volume; and c) a total pore volume of from about 45% to 86% of the total volume of the substrate particles.
The catalyst can be prepared by impregnating the support material with water-soluble compounds of nickel and/or cobalt and either molybdenum or tungsten as described in U.S. Pat. No. 5,820,749. Suitable catalyst supports are high surface area alumina such as xcex7-alumina and xcex3-alumina.
After impregnation, the support containing the nickel and/or cobalt and tungsten or molybdenum compounds is dried to remove the water from the impregnation solution. The dried support containing the nickel and/or cobalt and tungsten or molybdenum compounds is heat treated to decompose the nickel and/or cobalt and tungsten or molybdenum compounds to their oxide. Suitable temperatures range from about 300xc2x0 C. to about 550xc2x0 C. The amount of nickel oxide and/or cobalt oxide on the support ranges from 2% to 10% by weight. The amount of tungsten or molybdenum oxide on the support after preparation ranges from 5% to 25% by weight. Preferably the catalyst contains 4% to 7% by weight nickel oxide and 18% to 22% by weight tungsten oxide.
Typical activators for these catalysts include sulfiding agents in the presence of hydrogen. The sulfur compounds that can be used include H2S carbon disulfide, methyldisulfide, ethyldisulfide, propyldisulfide, isoporpyldisulfide, butyldisulfide, tertiary butyldisulfide, thianaphthene, thiophene, secondary dibutylsulfide, tertiary butylsulfide, dithiols and sulfur-bearing gas oils. Any other organic sulfur source that can be converted to H2S over the catalyst in the presence of hydrogen can be used. These catalysts can also be activated by an organo sulfur process as described in U.S. Pat. No. 5,530,917.
In addition a basic promoter may be used with the metal compounds, particularly if improved halogen resistance is sought. Promoters include metals form Groups 1-3, including the lanthanide and actinide series, of the periodic table of elements. The preferred promoters are typical lanthanum and potassium. The basic promoters may be used in amounts of 0.25% to 10% by weight of the total catalyst, preferably 1% to 3% by weight.
The hydrogenation process of this invention results in commercially acceptable resin decolorization while avoiding or significantly limiting cracking of the resin backbone due to acidic support surface and hydrochloric acid formation caused by resin dehalogenation. Because most of the halogen, typically chlorine, passes through the reactor rather than accumulating on the catalyst bed, not only is cracking reduced, but catalyst life is greatly extended.
After hydrogenation, the mixture from the reactor may be flashed and further separated to recover the solvent and hydrogen for recycle and to recover the hydrogenated resin. The resin solution is flashed and/or distilled in an oxygen free or minimum oxygen atmosphere to eliminate the solvent, and thereafter may be steam distilled to eliminate oligomers, preferably with care not to raise the temperature of the resin above 250xc2x0 C. to avoid degrading the color and other properties of the resin.
Resins thus obtained have a color of 5YI to 40YI depending on the initial color and on the resin structure. Using the process of this invention, the color is typically reduced by 30% to 80%, preferably by at least 40%, more preferably by at least 50%.
The softening point of the hydrocarbon resin produced using this hydrogenation process should not change by more than 8xc2x0 C., preferably not more than 5xc2x0 C., even more preferably not more than 3xc2x0 C. and most preferably there should be no detectable change in softening point of the resin before and after hydrogenation using the process of this invention.
In the process of this invention, the resins are hydrogenated such that at least 1.0% by weight of the carbon-carbon double bonds are reduced. In one embodiment at least 2.0% by weight of the carbon-carbon double bonds are reduced, and in another at least 2.5%, or even at least 3.0% by weight of the carbon-carbon double bonds are reduced.
The aromatic resins are hydrogenated such that the aromaticity level should not change by more than 5% by weight of equivalent styrene, preferably not more than 2%, even more preferably there should be no detectable change in aromaticity level of the aromatic resin before and after hydrogenation using the process of this invention.
Resin Aromaticity and carbon-carbon double bonds levels may be determined by 1H-NMR. Aromaticity is the integration of aromatic protons versus an internal standard (1,2 dichloroethane) given as weight percent of equivalent styrene, (104 g/mol). Carbon-carbon double bonds is the integration of olefinic protons versus an internal standard (1,2 dichloroethane) given as weight percent of equivalent xe2x80x94CHxe2x95x90CHxe2x80x94, (26 g/mol).
The resins obtained from this process preferably include hydrocarbon resins suitable as tackifiers for adhesive compositions, particularly adhesive compositions comprising polymeric base systems of either natural or synthetic elastomers including natural rubber, styrene block copolymers, ethylene-vinyl ester copolymers, metallocene polymers. Such compositions find particular utility in hot melt adhesive, pressure-sensitive adhesive and adhesive emulsions. Resins obtained from this process can also be used in road-marking compositions, as ink resins, as components in varnishes, paints and polymer modifiers.
The following examples are presented to illustrate the foregoing discussion. Although the examples may be directed to certain embodiments of the present invention, they are not to be viewed as limiting the invention in any specific respect.